MEDICAL IMAGING

RADIOLOGY• Radiology is a medical specialty that uses

imaging techniques to both diagnose and treat disease visualized within the human body.

• Imaging technologies include x-rays, ultrasound, computed tomography, nuclear medicine, positron emission tomography and magnetic resonance imaging, all of which are used to diagnose or treat diseases.

Ultrasounds• Use of sound above human

hearing range to image body structures, including soft tissues

• Sounds waves are reflected (echo) off of different density tissues differently

X-Rays

• Oldest form of imaging• Found by German physicist

Wilhelm Rontgen, 1895 • High-energy electromagnetic

waves that pass through soft tissue (ex. muscle) but are absorbed by dense tissue (ex. bone)

• Can also be used to see soft tissues with the help of stains (ex. bismuth)

Most popular use:

• Dental x-ray exposure can be minimal but concern over cumulative impact?

Electromagnetic radiation- Forms of energy, some on the visible spectrum

(light)

• Some can be damaging to our DNA, in particular high-energy high-frequency waves (above colour spectrum)

• X-rays is a type of ionising radiation

CAT Scans: computerized axial tomography scan

• An X-ray machine rotates around the patient taking hundreds of individual pictures form many angles

• More sensitive than an X-ray alone• Computer re-assembles the picture into a 3-D

image, allowing for organs to be viewed section-by-section

A CT or CAT scan (computed tomography) is a much more sensitive imaging technique than x-ray, allowing high definition not only of the bony structures, but of the soft tissues. Clear images of organs such as the brain, muscles, joint structures, veins and arteries, as well as anomalies like tumors and hemorrhages may be obtained with or without the injection of contrasting dye.

MRI

• Magnetic Resonance ImagingAn imaging technology that uses magnetism,

radio waves adn a computer to produce images of body structures.

The MRI scanner is a tube surrounded by a giant circular magent.

• The magnet creates a strong magnetic filed that aligns the protons of hydrogen atoms.

• The protons are then exposed to radio waves, which make them spin. This spinning produces a signal from which an image is produced.

What is MRI good for?

• Accurate disease detection throughout the body

e.g. tumours of the brain, inflammation of the spine, structure of the heart

CT vs. MRI

Depends on what is being diagnosed:

MRI - For brain tumour detection - For multiple exams

- Best for soft tissues (e.g heart)CT - For solid tumours in the chest and abdomen

- for bone abnormalities and injuries- cheaper than MRI

Nuclear Medicine Imaging

• Measures radiation emitted from within the body and provides information about the function of the organ, not just its structure

• Uses radioisotopes (unstable atoms) that are injected into the target organ for imaging

• Large amounts of isotopes collect at site of damage “lighting” it up

• Ex. PET scan: positron emission tomography

PET

Produces a three-dimensional image of functional processes in the body.

Gamma rays are emitted by a positron-emitting radionucleotide tracer, which is injected into the patient.

Used for imaging of tumours and metastases, also for brain and heart function

• PET scan are often used in combination with MRI or CT scans to give a complete metabolic and anatomic picture